Continuous action sheet press

ABSTRACT

A continuous action sheet press wherein the sheet material to be pressed is conducted into a gap between two moving surfaces, at least one of which is urged towards the sheet material to be pressed, by the aid of a pressure chamber. According to the invention the width of the pressure chamber varies in the direction of travel of the sheet material to be pressed.

United States Patent [1 1 Kerttula et al.

[ CONTINUOUS ACTION SHEET PRESS [22] Filed: Feb. 24, 1972 A 211 App]. o.=229,00s

[30] Foreign Application Priority Data 3,545,370 l2/l97O Caughey 425/l l X 3,617,594 ll/l97l Willy 425/115 X 3,044,111 7/1962 Caughey 425/371 X 3,296,658 1/1967 Buff et al. 425/371 X 2,331,145 /1943 Slayter..... 264/l09 X 2.697254 l2/l954 Gordon... 264/l l3 X 3,325,859 6/1967 Goldstein 425/371 X 3,568,245 3/l97l .Ietzer 425/115 X Primary Examiner-Robert L. Spicer, .Ir.

Feb. 25, Finland Att rney Eric H Waters et aL [52] US. Cl 425/371, 264/109, 264/113, [57] ABSTRACT 425/406 A t' act h t where'n th sh t 511 Int. Cl. B29j 5/04, B29c 3/00, B290 /00 9 ee Press e ee [58] Field of Search 425/335 338 371 terlal to be pressed lS conducted into a gap between "I two moving surfaces, at least one of which is urged 425/ 264/109 1 l 122 towards the sheet material to be pressed, by the aid of a pressure chamber. According to the invention the [56] References Clted width of the pressure chamber varies in the direction UNITED STATES PATENTS of travel of the sheet material to be pressed. 2,075,735 3 1937 Loomis 425/72 x 2,602,960 7/1952 Fischbein 8 Cla1ms,5 Drawmg Flgures 3,223,027 12/1965 Soda et al. 425/371 X I ""UUUUUUEIEIEUUUEJ Gm FATENTEDUEC 18 m3 saw 1 or 2 l. min

PRESSING TIME PATENTEDUEE 18 ms SHEET 2 [IF 2 CONTINUOUS ACTION SHEET PRESS A sheet press is here understood to refer to a press which may be employed for pressing sheets, such as plywood, chip, fibre and other boards, for laminating various kinds of sheets, for furnishing all kinds of sheets with a surface layer, etc. In all these instances the sheets have to be subjected to pressure. The sheets may be in the shape of a long web or of shorter pieces, which are consecutively fed into the press.

In order that the handling of the sheets to be manufactured or refined might be flexible and conveniently manageable, the trend has been to adopt continuous action presses instead of those which operate according to the batch principle. One such continuous action press wherein a pressure chamber is utilized has been disclosed in Swedish Patent No. 226,985. According to this patent, the pressure action upon the sheet material is constant, as a function of time. However, this is not favorable if the pressure remains constant throughout the time which the sheet spends in the press. In the manufacturing of chip boards, for instance, the pressure should first rise rather steeply up to its maximum and then decrease comparatively rapidly to about onetenth of the maximum and remain approximately at this value up to the end of the press time.

The object of the present invention is to furnish a continuous action press of the above-mentioned type and wherein the pressure varies as a function of time. The invention is characterized in that the width of the pressure chamber is variable in the direction of travel of the sheet material to be pressed. In a press according to the invention, the pressure is directly proportional to the width of the pressure chamber. The variations of this width, again, may be arranged to be appropriate for each individual intended pressing operation.

An advantageous embodiment of the invention is characterized in that between the pressure chamber and the sheet material to be pressed there are interposed transverse beams travelling along with the sheet material web and which extend over the total width of the sheet web. These beams transmit the pressure to be effective at those points where the pressure chamber has a width smaller than that of the sheet material web.

The invention is described in relation to several embodiments thereof with reference to the attached drawing, wherein FIG. 1 shows a pressure diagram which is appropriate when chip boards are being pressed,

FIG. 2 shows a press according to an advantageous embodiment of the invention, in longitudinal section taken along line lI-II of FIG. 3,

FIG. 3 shows the section taken along line III-III in FIG. 2,

FIG. 4 corresponds to FIG. 3 and shows another embodiment, and

FIG. 5 shows a section taken along line VV in FIG. 4.

Fig. 1 shows pressure diagram, representing pressure as a function of time, which is appropriate in a chip board manufacturing process. A pressure conforming to this diagram is obtained by means of a continuous action sheet press according to FIGs. 2 and 3. This press consists of two endless steel belts 1 and 2, which define between them a press gap. A chip mat 3, which has been provided with a bonding agent, is conducted into the press gap between the steel belts 1 and 2.

The compression acting upon the chip mat 3 is cre ated by means of a pressure chamber 41, into which a pressure medium, such as air, is introduced through the connector 6. As can be seen from FIG. 3, the shape of the pressure chamber 4 is equivalent to the pressure diagram of FIG. 1 taken together with its mirror image. As a result, the pressure acting upon the sheet web to be pressed, as a function of time, will conform to FIG. 1. The pressure chamber 4 is braced against the body of the press by transverse braces 5. The pressure is transmitted to the chip mat through an endless steel belt 7 encircling the pressure chamber 4, transverse beams 8 and the steel belt I. The purpose of the steel belt 7 is to seal the pressure chamber 4 on its underside. The purpose of the beams 8 is to spread the pressure to be effective over the entire width of the chip mat, because the pressure chamber 4 is not as wide thereas. The purpose of the steel belt 1 is to equalize the irregularities which might be caused in the surface of the chip mat to be pressed by the beams 8. The steel belts 7 and l have the same forward speed. These belts also determine the forward speed of the beams 8 and of the chip mat 3. As the beams 8 emerge, one after another, from the gap between the steel belts 7 and 1, they are picked up by a swivelling device 9, schematically depicted in the figure, which transfers them onto a conveyor 10 located overhead, which transports them to the initial end of the steel belt 7. Another swivelling device similar to the swivelling device 9 (not shown) is found here; said device picks up each beam 8 as it arrives and once more inserts it between the steel belts 7 and l. The conveyor 10 is downwardly sloping towards the inlet end of the press. Its speed is considerably higher than that of the steel belts 7 and 1. In the case illustrated in the figure, the speed of the conveyor 10 is so high that only two beams 8 at a time reside upon it. Hereby a small number of beams 8 will suffice.

According to FIGS. 2 and 3, the part of the press located under the chip mat 3 is identical to the part above this mat. But this is by no means absolutely necessary. It is essential that under the chip mat 3 there is a moving surface which takes up the pressure acting against the chip mat. This surface may even be curved and, for instance, consist of a rotating roll having a comparatively large diameter. If such is the case, the opposing surface must obviously also travel along a curved path.

The embodiment presented in FIGS. 4 and 5 is similar in principle to that shown in FIGS. 2 and 3. The difference is, however, that the ends of the pressure chamber 4 have been divided into three branches running in the longitudinal direction of the sheet web. It is hereby achieved that the pressure is more uniformly distributed on the beams 8, which therefore may be designed with lighter weight. Instead of three branches, the number of branches may also be two or, on the other hand, there may be more than three branches.

It is seen from FIGS. 4 and 5 that the side walls 11 of the pressure chamber 4 can be displaced in lateral direction by the aid of pressure cylinders 12. It is possible in this manner to change the shape of the pressure diagram as desired in each particular instance. The height of the press gap may be regulated by the aid of vertical tubes 13, which have been designed so that they can be telescopically lengthened and shortened.

It is obvious to one skilled in the art that different embodiments of the invention may vary within the scope of the claims presented below. For instance, the shape of the pressure chamber 4 is not confined to those embodiments which have been shown in FIGS. 3 and 4; instead, the pressure chamber will be designed to conform to the shape of the pressure diagram which is desired in each case. On the other hand, the transverse beams 8 shown in the drawing may be chain members belonging to an endless chain, or they may be omitted if the steel belt 1 is thick enough.

We claim:

1. A continuous action sheet press comprising two moving surfaces defining a press gap therebetween, the material to be pressed being conducted into said press gap to form a sheet therefrom, and a pressure chamber provided with pressure fluid acting on at least one of the moving surfaces to apply additional pressure to the material in the gap, said pressure chamber having a width which varies in the direction of travel of the material to be pressed.

2. A sheet press according to claim 1 comprising transverse beams interposed between the pressure chamber and the material to be pressed, and means for advancing the transverse beams along with the material, said transverse beams extending over the entire width of the sheet.

3. A sheet press according to claim 2 comprising a conveyor positioned adjacent said press gap to transfer the transverse beam at the discharge end of the press gap to the inlet end of the press gap.

4. A sheet press according to claim 3, wherein said conveyor has a speed of travel which is higher than the forward speed of travel of the sheet.

5. A sheet press according to claim 2, wherein the transverse beams traveling with the sheet are chain members of an endless chain.

6. A sheet press according to claim 1, wherein the pressure chamber is divided into at least two branches extending longitudinally of the sheet. A sheet press according to claim 1, wherein said pressure chamber includes walls which are displaceable in a direction transverse to the sheet.

8. A sheet press according to claim 8, wherein said width of the pressure chamber diminishes substantially in the direction of travel of the material. 

1. A continuous action sheet press comprising two moving surfaces defining a press gap therebetween, the material to be pressed being conducted into said press gap to form a sheet therefrom, and a pressure chamber provided with pressure fluid acting on at least one of the moving surfaces to apply additional pressure to the material in the gap, said pressure chamber having a width which varies in the direction of travel of the material to be pressed.
 2. A sheet press according to claim 1 comprising transverse beams interposed between the pressure chamber and the material to be pressed, and means for advancing the transverse beams along with the material, said transverse beams extending over the entire width of the sheet.
 3. A sheet press according to claim 2 comprising a conveyor positioned adjacent said press gap to transfer the transverse beam at the discharge end of the press gap to the inlet end of the press gap.
 4. A sheet press according to claim 3, wherein said conveyor has a speed of travel which is higher than the forward speed of travel of the sheet.
 5. A sheet press according to claim 2, wherein the transverse beams traveling with the sheet are chain members of an endless chain.
 6. A sheet press according to claim 1, wherein the pressure chamber is divided into at least two branches extending longitudinally of the sheet.
 7. A sheet press according to claim 1, wherein said pressure chamber includes walls which are displaceable in a direction transverse to the sheet.
 8. A sheet press according to claim 8, wherein said width of the pressure chamber diminishes substantially in the direction of travel of the material. 